学步园

这里实现了一个Rotate3dAnimation的类，它扩展了Animation类，重写applyTransformation()方法，提供指定时间的矩阵变换，我们在这个方法里，就可以利用Camera类得得到一个围绕Y轴旋转的matrix，把这个matrix设置到Transformation对象中。  具体的实现代码如下：

@Override
protected void applyTransformation(float interpolatedTime, Transformation t)
{
        final float fromDegrees = mFromDegrees;
        float degrees = fromDegrees + ((mToDegrees - fromDegrees) * interpolatedTime);

        final float centerX = mCenterX;
        final float centerY = mCenterY;
        final Camera camera = mCamera;

        final Matrix matrix = t.getMatrix();

        camera.save();
        if (mReverse) {
            camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);
        } else {
            camera.translate(0.0f, 0.0f, mDepthZ * (1.0f - interpolatedTime));
        }
        camera.rotateY(degrees);
        camera.getMatrix(matrix);
        camera.restore();

        matrix.preTranslate(-centerX, -centerY);
        matrix.postTranslate(centerX, centerY);
}

2，如何使用这个动画类

在Activity中，我们有两个大小一样的ImageView，它们都放在FrameLayout中，这样他们位置是重叠的，对最上面的ImageView做动画（旋转角度从0到90），当动画做完后，再对后面的ImageView做动画（旋转角度从90到180），在这里，要控制相应的ImageView隐藏或显示。

动画的listener实现如下： 

private final class DisplayNextView implements Animation.AnimationListener {

        public void onAnimationStart(Animation animation) {
        }

        public void onAnimationEnd(Animation animation) {

            mContainer.post(new SwapViews());
        }

        public void onAnimationRepeat(Animation animation) {
        }
    }

动画做完后，执行的代码如下：

private final class SwapViews implements Runnable
    {
        @Override
        public void run()
        {
            mImageView1.setVisibility(View.GONE);
            mImageView2.setVisibility(View.GONE);

            mIndex++;
            if (0 == mIndex % 2)
            {
                mStartAnimView = mImageView1;
            }
            else
            {
                mStartAnimView = mImageView2;
            }

            mStartAnimView.setVisibility(View.VISIBLE);
            mStartAnimView.requestFocus();

            Rotate3dAnimation rotation = new Rotate3dAnimation(
                    -90,
                    0,
                    mCenterX,
                    mCenterY, mDepthZ, false);

            rotation.setDuration(mDuration);
            rotation.setFillAfter(true);
            rotation.setInterpolator(new DecelerateInterpolator());
            mStartAnimView.startAnimation(rotation);
        }
    }

点击Button的事件处理实现:

            @Override
            public void onClick(View v)
            {
                mCenterX = mContainer.getWidth() / 2;
                mCenterY = mContainer.getHeight() / 2;

                getDepthZ();

                applyRotation(mStartAnimView, 0, 90);
            }

applyRotation的实现如下：

private void applyRotation(View animView, float startAngle, float toAngle)
    {
        float centerX = mCenterX;
        float centerY = mCenterY;
        Rotate3dAnimation rotation = new Rotate3dAnimation(
                startAngle, toAngle, centerX, centerY, mDepthZ, true);
        rotation.setDuration(mDuration);
        rotation.setFillAfter(true);
        rotation.setInterpolator(new AccelerateInterpolator());
        rotation.setAnimationListener(new DisplayNextView());

        animView.startAnimation(rotation);
    }

public class Rotate3dAnimActivity extends Activity
{
    ImageView mImageView1 = null;
    ImageView mImageView2 = null;
    ImageView mStartAnimView = null;
    View mContainer = null;
    int mDuration = 500;
    float mCenterX = 0.0f;
    float mCenterY = 0.0f;
    float mDepthZ  = 0.0f;
    int mIndex = 0;
    
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        
        setContentView(R.layout.rotate_anim);
        
        mImageView1 = (ImageView) findViewById(R.id.imageView1);
        mImageView2 = (ImageView) findViewById(R.id.imageView2);
        mContainer  = findViewById(R.id.container);
        mStartAnimView = mImageView1;
        
        findViewById(R.id.button1).setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                mCenterX = mContainer.getWidth() / 2;
                mCenterY = mContainer.getHeight() / 2;
                
                getDepthZ();
                
                applyRotation(mStartAnimView, 0, 90);
            }
        });
        
        InputMethodManager imm = (InputMethodManager)getSystemService(INPUT_METHOD_SERVICE);
        imm.hideSoftInputFromWindow(getWindow().getDecorView().getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);
    }
    
    private void getDepthZ()
    {
        EditText editText = (EditText) findViewById(R.id.edit_depthz);
        String string = editText.getText().toString();
        
        try
        {
            mDepthZ = (float)Integer.parseInt(string);
            //mDepthZ = Math.min(mDepthZ, 300.0f);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
    
    private void applyRotation(View animView, float startAngle, float toAngle)
    {
        float centerX = mCenterX;
        float centerY = mCenterY;
        Rotate3dAnimation rotation = new Rotate3dAnimation(
                startAngle, toAngle, centerX, centerY, mDepthZ, true);
        rotation.setDuration(mDuration);
        rotation.setFillAfter(true);
        rotation.setInterpolator(new AccelerateInterpolator());
        rotation.setAnimationListener(new DisplayNextView());
        
        animView.startAnimation(rotation);
    }
    
    /**
     * This class listens for the end of the first half of the animation.
     * It then posts a new action that effectively swaps the views when the container
     * is rotated 90 degrees and thus invisible.
     */
    private final class DisplayNextView implements Animation.AnimationListener {

        public void onAnimationStart(Animation animation) {
        }

        public void onAnimationEnd(Animation animation) {
            
            mContainer.post(new SwapViews());
        }

        public void onAnimationRepeat(Animation animation) {
        }
    }
    
    private final class SwapViews implements Runnable
    {
        @Override
        public void run()
        {
            mImageView1.setVisibility(View.GONE);
            mImageView2.setVisibility(View.GONE);
            
            mIndex++;
            if (0 == mIndex % 2)
            {
                mStartAnimView = mImageView1;
            }
            else
            {
                mStartAnimView = mImageView2;
            }
            
            mStartAnimView.setVisibility(View.VISIBLE);
            mStartAnimView.requestFocus();
            
            Rotate3dAnimation rotation = new Rotate3dAnimation(
                    -90, 
                    0, 
                    mCenterX,
                    mCenterY, mDepthZ, false);
            
            rotation.setDuration(mDuration);
            rotation.setFillAfter(true);
            rotation.setInterpolator(new DecelerateInterpolator());
            mStartAnimView.startAnimation(rotation);
        }
    }
}

rotate_anim.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:text="Do 3d animation" />
    
    <TextView 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20px"
        android:text="Input Depth on Z axis. [0, 300]"
        />
    <EditText 
        android:id="@+id/edit_depthz"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:text="0"/>

    <FrameLayout 
        android:id="@+id/container"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
       <ImageView
        android:id="@+id/imageView1"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_margin="20dp"
        android:src="@drawable/f" />
       
       <ImageView
        android:id="@+id/imageView2"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_margin="20dp"
        android:src="@drawable/s" 
        android:visibility="gone"/>
        
    </FrameLayout>

</LinearLayout>

package com.nj1s.lib.anim;

import android.graphics.Camera;
import android.graphics.Matrix;
import android.view.animation.Animation;
import android.view.animation.Transformation;

/**
 * An animation that rotates the view on the Y axis between two specified angles.
 * This animation also adds a translation on the Z axis (depth) to improve the effect.
 */
public class Rotate3dAnimation extends Animation {
    private final float mFromDegrees;
    private final float mToDegrees;
    private final float mCenterX;
    private final float mCenterY;
    private final float mDepthZ;
    private final boolean mReverse;
    private Camera mCamera;

    /**
     * Creates a new 3D rotation on the Y axis. The rotation is defined by its
     * start angle and its end angle. Both angles are in degrees. The rotation
     * is performed around a center point on the 2D space, definied by a pair
     * of X and Y coordinates, called centerX and centerY. When the animation
     * starts, a translation on the Z axis (depth) is performed. The length
     * of the translation can be specified, as well as whether the translation
     * should be reversed in time.
     *
     * @param fromDegrees the start angle of the 3D rotation
     * @param toDegrees the end angle of the 3D rotation
     * @param centerX the X center of the 3D rotation
     * @param centerY the Y center of the 3D rotation
     * @param reverse true if the translation should be reversed, false otherwise
     */
    public Rotate3dAnimation(float fromDegrees, float toDegrees,
            float centerX, float centerY, float depthZ, boolean reverse) {
        mFromDegrees = fromDegrees;
        mToDegrees = toDegrees;
        mCenterX = centerX;
        mCenterY = centerY;
        mDepthZ = depthZ;
        mReverse = reverse;
    }

    @Override
    public void initialize(int width, int height, int parentWidth, int parentHeight) {
        super.initialize(width, height, parentWidth, parentHeight);
        mCamera = new Camera();
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        final float fromDegrees = mFromDegrees;
        float degrees = fromDegrees + ((mToDegrees - fromDegrees) * interpolatedTime);

        final float centerX = mCenterX;
        final float centerY = mCenterY;
        final Camera camera = mCamera;

        final Matrix matrix = t.getMatrix();

        camera.save();
        if (mReverse) {
            camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);
        } else {
            camera.translate(0.0f, 0.0f, mDepthZ * (1.0f - interpolatedTime));
        }
        camera.rotateY(degrees);
        camera.getMatrix(matrix);
        camera.restore();

        matrix.preTranslate(-centerX, -centerY);
        matrix.postTranslate(centerX, centerY);
    }
}

各位，请想一想，为实现applyTransformation方法时，最后的为什么要有这两句话：

        matrix.preTranslate(-centerX, -centerY);
        matrix.postTranslate(centerX, centerY);